FIG. 1 is a view showing change in an angle of light incident on a sensor through an external lens in a range from the center to the edge of a pixel area; In general, an angle of light increases linearly up to saturated angle, and after that, decreases in the edge area.
FIG. 2 is a view showing optical paths of light incident on the center area and on the edge area of the external lens.
When the centers of the micro lens and the photodiode are coincident with each other in the edge area, a focusing rate oh the photodiode decreases.
FIG. 3 is a view showing a shift state of a micro lens for focusing light incident on the micro lens on a photodiode in the edge area.
If the micro lens is not shifted so as to focus a light incident on the micro lens on the photodiode in the edge area, the incident light cannot be focused on the photodiode.
Besides, most optical lenses used in mobile phones are aspheric lenses. So the light with nonlinear ratio of angle of light to an image field is incident on the sensor.
In order to solve the problems, in production of micro lenses pitches of the micro lenses are designed to be smaller than a pixel pitch, so that the micro lenses in the edge area are shifted to the center direction of the photodiodes PD to focus light on the photodiodes.